obama stops in des moines, iowa and richmond, virginia. >>> at the white house, the obama administration faces a big staff shake-up, the latest may involve the chief of staff. as bill plante reports, personnel changes are nothing new for any president. >> reporter: they are breaking up the old gang at the white house. it's that time again, about two years into any president's first term and the staff starts heading for the exits. >> two years, people start to leave. they burn themselves out, they work very hard and have jobs they can't refuse on the outside. >> reporter: the chief of staff rahm emanuel may leave as soon as next month to run for mayor of chicago. the big question, does the president look inside or outside to replace him. >> is he just drawing the wagons around him, or is he reaching out in which he's saying, hey, i think there are different ways to do it? >> reporter: defense secretary robert gates and national security adviser james jones are also expected to leave sometime next year. national economic council head larry summers going back to harvard. other members of th